Analysis of the cellular and molecular mechanisms mediating peptide hormone action constitutes an important component of our research efforts. The close interrelationships mediating neuroendocrine responses within the hypothalamic-pituitary- gonadal system offer an excellent opportunity to analyze some unique characteristics of peptide-peptide, peptide-amine, and peptide-amine-steroid interactions. Studies using pituitary cell cultures were directed to evaluate the precise mechanisms through which peptidergic or aminergic secretagogues enhance or suppress peptide hormone release. A main target of our research efforts has been to analyze the role of hormonal input signal in modifying cellular responses, using a computerized perfusion system that can exquisitely regulate the delivery of appropriately-designed hormone signals to cells or tissues (in vitro). Other protocols were designed to evaluate characteristics of hormone-receptor interactions (post-receptor as well as transmembrane events involved in the hormone-release process) and definition of the specific intracellular messengers transducing the action of key hypothalamic peptides involved in pituitary hormone release. In order to understand the role of pulsatile hormone secretion in providing coded messages for the activation of endocrine target tissues, experiments were designed and carried out to analyze the pulsatile pattern of secretion of different peptide hormones (LHRH, LH, ACTH, Prolactin) intimately involved in the regulation of endocrine and reproductive functions. The characteristic pattern of secretion of each hormone was defined as well as the role of certain neural or gonadal factors in modulating the pulsatile pattern. The information obtained provides a more clear understanding of the mechanisms regulating episodic hormone secretion.